If [code]true[/code], the sub-viewport will be used in AR/VR process. The clear mode when the sub-viewport is used as a render target. The update mode when the sub-viewport is used as a render target. The width and height of the sub-viewport. The 2D size override of the sub-viewport. If either the width or height is [code]0[/code], the override is disabled. If [code]true[/code], the 2D size override affects stretch as well. Do not update the render target. Update the render target once, then switch to [constant UPDATE_DISABLED]. Update the render target only when it is visible. This is the default value. Update the render target only when the its parent is visible. Always update the render target. Always clear the render target before drawing. Never clear the render target. Clear the render target next frame, then switch to [constant CLEAR_MODE_NEVER].